[Diminished fertility in seals in the Netherlands, possibly resulting from exposure to large amounts of polychlorinated biphenyls (author's transl)].

The number of seals in the coastal waters of the Netherlands has been considerably reduced since 1950: in the Wadden Sea, it decreased from 3,000 to 500, in the Delta area, from 1,500 to merely a few animals. Studies on population dynamics during the period from 1974 to 1978 showed that reproduction among the seal population in the Netherlands Wadden Sea is too small compared with the stable population of Schleswig-Holstein. Investigations on the role of environmental factors in diminished reproduction centered on the factor water pollution. Analysis of the various contaminants in the tissues of seals of the Netherlands. Schleswig-Holstein and Denmark, which were found dead, showed tha particularly the concentrations of polychlorinated biphenyls in seals of the Netherlands were significantly higher than they were in German and Danish animals. The epidemiological and experimental findings on the characteristics of these contaminants, in conjunction with the high concentrations of polychlorinated biphenyls and the decrease in reproduction of seals in the Netherlands, led to the hypothesis that polychlorinated biphenyls are the cause of diminished fertility of seals in the Netherlands.